1. Field of the Invention
The present invention relates to a transmitting display panel employed for various displaying purposes or advertisement and the like purposes, and particularly to a display panel in which a display pattern involving characters, figures or pictures is formed on a transparent substrate in accordance with transferring technique as well as a process for forming such pattern.
2. Description of the Prior Art
A display panel provided with a plurality of printing ink layers on the substrate thereof can be produced in such a way that a transfer sheet in which a printing ink layer is formed on a pulpboard sheet by the use of a water-resistant printing ink in accordance with printing operation is bonded to the transparent substrate by utilizing an adhesive so as to closely adhere the printing ink layer to the back of the substrate; thereafter, the pulpboard sheet is dissolved and removed to leave the printing ink layer, and further such transferring operation is repeated by a required number of times. This type of display panel has an equivalent clear picture to that of a printing paper, besides the display panel has favorable transmission, water resistance, shape retention and the like so that such display panel is suitable for the use of illuminating advertisement board and the like. However, in such display panel, there are many cases where rainbow-like design appears in a fine pattern such as textile or a part of half tone such as flesh color so that displaying effects of the display panel decrease.
It is difficult to apply a process for forming an arbitrary pattern on the surface of an article made from most plastic material which does not absorb printing ink. Furthermore a pattern formed on the surface of such article by means of printing operation is inferior to a pattern printed on a paper sheet from the viewpoints of fineness, color tone and the like. Application of photographic technique is practised for the same purpose, but a pattern formed by developing a sensitized material is remarkably unfavorable in the discoloration thereof so that its initial quality cannot be maintained for a long period of time.